Comparing high-latitude thermospheric winds from Fabry–Perot interferometer (FPI) and challenging mini-satellite payload (CHAMP) accelerometer measurements

Aruliah, Anasuya; Förster, Matthias; Hood, Rosie; McWhirter, Ian; Doornbos, Eelco

doi:https://doi.org/10.5194/angeo-37-1095-2019

Articles | Volume 37, issue 6

https://doi.org/10.5194/angeo-37-1095-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/angeo-37-1095-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 37, issue 6

Regular paper

|

10 Dec 2019

Regular paper |

| 10 Dec 2019

Comparing high-latitude thermospheric winds from Fabry–Perot interferometer (FPI) and challenging mini-satellite payload (CHAMP) accelerometer measurements

Anasuya Aruliah, Matthias Förster, Rosie Hood, Ian McWhirter, and Eelco Doornbos

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Final revised paper (published on 10 Dec 2019)
Preprint (discussion started on 29 Apr 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Revisions are needed.', Anonymous Referee #1, 09 May 2019
- AC1: 'CHAMP-FPI paper response to referee 1', Anasuya Aruliah, 21 Aug 2019
- AC2: 'CHAMP-FPI paper response to referee 2', Anasuya Aruliah, 21 Aug 2019
RC2: 'Manuscript Review: Comparing high-latitude thermospheric winds from FPI and CHAMP accelerometer measurements', Anonymous Referee #2, 31 May 2019
- AC2: 'CHAMP-FPI paper response to referee 2', Anasuya Aruliah, 21 Aug 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by editor and referees) (21 Aug 2019) by Christoph Jacobi

AR by Anasuya Aruliah on behalf of the Authors (21 Aug 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (27 Aug 2019) by Christoph Jacobi

RR by Anonymous Referee #1 (04 Sep 2019)

Suggestions for revision or reasons for rejection

Dear Editor,

The revised paper has improved greatly. However, I still have some issues in the current version. Since I did not raise those issues earlier, I am not going to insist revisions to the paper. With the exception of the Equ 2, I think should be revised.
I still don’t understand the rational for including the U.Alaska FPI data in the discussion here.
“The calibration of FPIs is an important section attempting to understand the discrepancy in the CHAMP-FPI winds. The University of Alaska FPI measurements at Longyearbyen, made in the early 1980s, are used to show that their FPI measurements are consistent in phase with the UCL FPI measurements 20 years later. They are also of a magnitude closer to the UCL FPI than the CHAMP winds. Even then Hedin et al. (1991) noted that the U.Alaska ground-based FPI zonal wind magnitudes in 1980 showed smaller magnitudes than satellites.”
I don’t think you need almost 40-year old U.Alaska data to prove the UCL FPI data are of good quality. You have many publications in the past using the UCL FPI data, which should be sufficient to prove you have good data set. Most of FPIs do not have 40-year data to compared with.
Here you still have another loose end. “Even then Hedin et al. (1991) noted that the U.Alaska ground-based FPI zonal wind magnitudes in 1980 showed smaller magnitudes than satellites. “
Thirty years ago, we did not have accelerometer data to compare with. Hedin et al. were talking about the comparisons between the wind data from DE-2, which is a combination of the FPI and WATS in-situ observation. If there were discrepancy between ground-based and satellite observations then, that was a totally different comparison with different technologies. It is hard to relate that discrepancy with the one at hand.
The paper is a little bit unbalanced. The paper is more focused on possible issues related to the FPI but not so much with CHAMP data. It should be obvious that the issue is with CHAMP. Perhaps, the authors should at least promise something to be done in future studies.
The Song (2009) paper does not add much to the discussion about the discrepancy. Same for the Vadas and Crowley’s paper. Those two papers were not well explained. I leave the authors to decide to keep them or not.
The last sentence is pretty vague “We may also need to rethink the procedure of comparing different spatial and temporal resolutions of in-situ satellite versus remote ground-based FPI measurements in terms of the geometry of cross-track winds at high latitudes. “If you have issue with the CHAMP winds, then changing geometry is not going to fix the problem.
I still don’t see how Equ 2 is the same as the authors showed in the reply. If you just copy what you have in the reply, it will be fine. The formula in the paper is not clear.

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RR by Anonymous Referee #2 (26 Sep 2019)

ED: Publish subject to revisions (further review by editor and referees) (27 Sep 2019) by Christoph Jacobi

AR by Anasuya Aruliah on behalf of the Authors (18 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (21 Oct 2019) by Christoph Jacobi

RR by Anonymous Referee #2 (23 Oct 2019)

ED: Publish as is (24 Oct 2019) by Christoph Jacobi

AR by Anasuya Aruliah on behalf of the Authors (27 Oct 2019)

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Anasuya Aruliah on behalf of the Authors (09 Dec 2019) Author's adjustment Manuscript

EA: Adjustments approved (09 Dec 2019) by Christoph Jacobi

Short summary

Winds near the top of the atmosphere are expected to be the same at all heights for a given location by assuming high viscosity in rarefied gases. However, wind measurements from satellite drag at 350–400 km altitude were found to be up to 2 times larger than optical measurements at ∼240 km. Satellites provide global measurements, and ground-based FPIs provide long-term monitoring at single sites. So we must understand this inconsistency to model and predict atmospheric behaviour correctly.